Seeking advice regarding Storyline online training

Hi everyone! I was looking at some different online courses for more advanced Storyline training and wanted to get input from my fellow Storyline lovers! I am interested in online training, and have been using the program for over a year now, so I am pretty comfortable with using it. I do feel that there is more to learn, though, and am hoping to find an online course that will really be able to show me some different ways of doing things and increase my present knowledge, which I would say is intermediate, to expert!

Does anyone have any advice about training programs,maybe using their own experience? I was looking at Lodestone's online Articulate Storyline Intermediate course. This one looks pretty good, but by what I have read it may go over a lot of things that I already have a handle on.

Also, can anyone tell me what a custom Preloader is?

Thanks for any help you can send my way!

Debra